When we see records being broken and unprecedented events such as this, the onus is on those who deny any connection to climate change to prove their case. Global warming has fundamentally altered the background conditions that give rise to all weather. In the strictest sense, all weather is now connected to climate change. Kevin Trenberth

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Cryosat, the latest in a series of ice-monitoring satellites, has been measuring the decline of Arctic Sea ice using radar for more than two years. In addition to tracking the record-breaking loss of ice during summer months, this satellite also looked at how well the ice recovered during winter freeze-up. What it found is the growth in winter is not matching the summer loss.

Previous measurements have mostly tracked the area covered by the ice, but thanks to Cryosat, they have been able to measure the loss in volume, which is a much more accurate measurement of what's happening to the Arctic ice. Since 2003, the volume of ice has declined 36% in autumn and 9% in winter.

Meanwhile, Canadian and American scientists have been cruising Arctic waters since 2003 on Canadian ice-breakers, tracking the ice conditions from the surface to compare it to the satellite data. One of the problems with observations from space is that an instrument looking down from above can only see differences between one area and another. In order to know exactly what it's seeing, to establish a baseline from which those differences can be understood, there needs to be "ground truthing." That's where the same piece of the Earth is looked at from above and from the surface to get the most accurate picture of what's going on.

But now, thanks to new confidentiality rules introduced into the U.S.-Canada project, both the Canadian scientists working at the Department of Fisheries and Oceans and the Americans may not be able to publish or distribute that data without government approval. Is this yet another example of environmental scientists being restricted by the government from distributing their own work?

The original U.S.-Canada agreement on this project, signed in 2003, contained a clause that allowed free dissemination and publication of information to anyone at any time. But the new agreement asks the Americans to hold back their publications until they get agreement from Canada, which they find intolerable. And rightly so. How can Canada restrict the actions of scientists working in another country?

American scientists have refused to sign, and negotiations are under way to solve the dispute.